Tanning



Patented May 17, 1938 PATENT OFFICE TANNING Gustav Mauthe and Hermann Noerr, Leverkusen I. G. Wei-k, Germany, assignors to]. G. Farbenindustrie Aktiengesellschaft, Frankfort-on the-Main, Germany N Drawing; Application November 21, 1935, Serial No. 50,988. In Germany November 24,

- 6 Claims. (01. 149-4) However, the afllnity of zirconiumchlorides for the animal skin fiber is rather small. Therefore,

by the previously described tanning process making use of zirconiumchloride, it was not possible to prepare thoroughly tanned leathers; on the contrary, the products obtained according to the said process are still of horny, parchment-like character and swell easily when treated with hot 'water. I f

It is the object of our invention to improve tanning with zirconiumchlorides to such a de- 5 g1'ee that the resulting leathers will stand any competition in the market, thereby for the first time making practically possiblethe use of zirconiumchlorides in the leather industry, an

achievement highly desirable for the above and 30 other reasons.

This object we attain by performing the tanning with zirconiumchlorides in the presence of sulfate ions, which are incorporated with the tanning liquor, for instance, by adding thereto 5 compounds yielding sulfate ions. Primarily sulfuric acid or watersoluble sulfates such, for instance, as sodium, potassium or aluminium sulfates may be mentioned as suitable compounds yielding sulfate ions, it being understood, how- 40 ever, that they are mentioned here only for examples sake; so, if no value is set on a white color of the leathers, chromium sulfates may be employedtoo. Furthermore, the said and other like sulfate compounds can be added alone or in com- 5 bination with neutral salts.

Thequantity of sulfate compounds and also the manner of adding the same can vary somewhat, depending on the nature and kind of hides and the special 'tanningtprocess employed. As

- 5 will be seen from the following examples they can easily be so chosen, however, by anyone skilled in' the art, as to secure the optimum aflinity of the tanning agent for the skin fiber. If, for instance, heavy hides are to be tanned, it is pref- 55 erable to gradually add asulfate or other substance yielding sulfate ions durlng the tannage,

, an amount of more than about 1% (calculated on the hide weight) being preferred. Tanning will then proceed, softly and rapidly. On the other hand, with light skin material the whole amount of neutral salts necessary in order to prevent swelling can be added at the beginning in the form of water-soluble sulfates, for example, sodium sulfate.

In addition to the advantage of using the easily obtainable zirconiumchlorides and, furthermore, the great adaptability to the kind of skin and the'tanning process employed, it is another great advantage of our new process that, in comparison with the zirconium sulfate tannage, our process can be performed at much higher basicity. For as is seen from the above formula, the easily water-soluble zirconiumchloride is 50% basic, a basicity not to be attained, for instance, with zirconium sulfate, as the corresponding basic sulfates are not soluble. But in spite of the, high basicity the tanning according to our present process is a' mild one, especially if greater quantities of sulfate ions are employed, and yields full leathers of very fine grain. Besides, the quantity of the neutralizing agents to be added in the usual way at the end of the tannage in order to render the skin weakly acid, is considerably smaller than the'quantity necessary, for instance,

in a zirconium sulfate tannage.

Our present process can be performed alone or in combination with other usual tanning processes.

The leathers obtainable according to our new process are distinguished by their great fullness, light color and extraordinary fastness to light.

,The following examples'illustrate the invention without limiting it thereto, the indications in per cent being calculated upon the weight of the unhaired hides:-

Example 1 neutralized with an aqueous solution of about 1% page is continued for 3 hours further.

of sodiumbicarbonate until the reaction is only weakly acid to Congo red. The leathers are then beaten on the jack over night and rinsed the next day until the leather cut shows a pH value of 4.5;

they are then greased with a light-colored watersoluble fat and pole-dried. The finished leather shows a fine grain, a good fullness and a white color. 1

Example 2 anhydrous sodium sulfate is dissolved in water and divided into four parts and added with intervals of an hour. Drumming is continued for one to two hours. A streak cut from the leather and laid in water no longer shows any untanued swelling zone. with 0.6% aqueous solution of sodium bicarbonate. The leather is then beaten on the jack over night, rinsed in, the drum withrunning water, greased, dried and worked up in the usual manner. The hydrochloric acid pickle may be replaced by a pickle of formic acid and sodiumchloride.

Examp'le 3 Heavy calf hides which have been thoroughly pickled with hydrochloric acid are tanned with 7.8% of zirconiumoxychloride (3% of zirconiumdioxide), which, before adding to the tanning liquor, has been brought.to a basicity of 25% with the aid of hydrochloric acid, in 100% of water in which 8% of anhydrous sodium sulfate is dissolved. The tanning agent is gradually added and tannage is continued until the thickest parts of the hides are thoroughly tanned. The liquor is neutralized with an aqueous solution of sodium bicarbonate until the reaction to Congo red is only weakly acid.

Example 4 A goat hide is cut in two halves and tanned in accordance with the manner described in Example 2 with the quantity of zirconiumoxychloride which corresponds to 2.5% of zirconiumdioxide. Instead of the addition of sodium sulfate .as described in Example 2, (a) 6% of potassium sulfate or (b) 8% of aluminium sulfate is gradually added. In either case the tannage is continued until the zirconium reaction is negative, when a thorough tanning is achieved. The liquor is then neutralized and the leathers are worked up in the usual manner. In both cases, very fine, soft and full leathers are obtained.

The liquor is then neutralized Example 5 umoxychloride, 1% of formic acid (technical 85%), 40% of anhydrous sodium sulfate.

After the leather is thoroughly tanned it is well rinsed, fatted, dried, moistened, dressed and tacked.

Emample 6 Cow hides are well pickled with hydrochloric acid and treated in the suspender with a liquor of the following composition: 200% of water, 5% of zirconiumoxide in the form of zirconiumoxychloride, 20% of anhydrous sodium sulfate and 2% of technical hydrochloric acid (22%).

After two to three days the hides are thoroughly tanned. They are freed from the acid by washing with water, oiled off, tacked and dried.

We claim:-

l. In'the process of tanning with zirconium salts, the modification which comprises treating pickled hides of acid reaction with a solution containing a water-soluble zirconium chloride and gradually adding thereto a water-soluble sulfate during tannage.

2. In the process of tanning with zirconium salts, the modification which comprises treating pickled hides of acid reaction with a solution containing a water-soluble zirconium chloride and gradually adding thereto a water-soluble sulfate during tannage so that at the end more than about 1% of sulfate ions are present in the solution.

3. In the process of tanning with zirconium salts, the modification which comprises dissolving a water-soluble zirconium chloride and a watersoluble compound yielding sulfate ions in an aqueous medium, and tanning. pickled hides of acid reaction therein.

4. In the process of tanning a water-soluble zirconium chloride and a waterwith zirconium salts, the modification which comprises dissolving soluble sulfate in an aqueous medium, and tanning pickled hides of acid reaction therein.

5. In the process of tanning with zirconium salts, the modification which comprises dissolving a water-soluble zirconium chloride and a water-:- soluble sulfate selected from the group consisting of alkali metaland ammonium sulfates in an aqueous medium, and tanning pickled hides of acid reaction therein.

6. In.the process of tanning with zirconium salts, the modification which comprises dissolving zlrconiumoxychloride (ZrOClz.aq) and a watersoluble sulfate selected from the group consisting of alkali metal and ammonium sulfates in an aqueous medium, and tanning pickled hides of acid reaction therein.

GUSTAV MAU'I'HE. HERMANN NOERR. 

